Biomedical Frontiers: Fall 1997, Vol.4, No.2
Diabetes Research
A Connection to Obesity

The effect of increased weight on the risk of developing diabetes.

Researchers have long known that obesity is a risk factor for diabetes. At the Obesity Research Center at St. Luke's-Roosevelt Hospital Center, researchers are gaining a better understanding of the connection between the two conditions.

In the 1980s, studies first indicated clearly that not only is obesity a risk factor for diabetes, but the distribution of fat in the body also plays a role. Fat that is centrally located poses a greater risk of diabetes, says Dr. F. Xavier Pi-Sunyer, director of the Obesity Research Center, chief of endocrinology, diabetes, and nutrition at St. Luke's-Roosevelt and professor of medicine at Columbia University. For instance, recent studies by Drs. Pi-Sunyer and Jeanine Albu, assistant professor of medicine, have found that for equivalent amounts of fat, women who gain weight in the central visceral area are at higher risk for diabetes than women who gain weight on the hips and buttocks. Also, they have found that for a given level of obesity, black women are less at risk than white women because they have less central visceral fat.

The insulin receptor and its signalling.

The researchers are now studying the response of fat cells from various regions of the body to agents that stimulate or inhibit lipolysis (the release of fat from cells). "Centrally located fat may be more sensitive to lipolysis and therefore may be more prone to release fatty acids," says Dr. Pi-Sunyer. "These cells may also be less sensitive to insulin, which tends to inhibit fat release." In addition, lipolysis, by elevating circulating fatty acids, can enhance the production of abnormal lipid levels by the liver and can stimulate glucose production by the liver while inhibiting glucose uptake by the muscles--factors that predispose individuals to diabetes. Finally, increased amounts of central body fat decrease the ability of the liver to degrade insulin. High levels of insulin have been implicated in atherogenesis.

The St. Luke's-Roosevelt Obesity Research Center is the only NIH-sponsored center in New York state devoted to the study of obesity and its etiology. It is one of 25 centers now involved in the seven-year NIH Diabetes Prevention Trial, a nationwide study aimed at preventing diabetes. This research is only part of the many programs in obesity and diabetes that Dr. Pi-Sunyer and colleagues are involved in.